Small electronic components, including amplifiers, filters, transducers and the like, are employed in a number of devices, particularly in radio frequency (RF) wireless communications, for example. Various types of filters, for example, include acoustic filters, such as surface acoustic wave (SAW) resonator devices containing SAW resonators, and bulk acoustic wave (BAW) resonator devices containing thin film bulk acoustic resonators (FBARs) and solidly mounted resonators (SMRs), for example.
Conventionally, the electronic components are combined in circuit packages and covered with external shields to form discrete shielded packages, referred to as “modules.” The external shields are generally shield layers that cover the top and sidewalls of the circuit packages, and provide protection against externally generated electromagnetic radiation (“external electromagnetic radiation”), as well as and environmental stresses, such as temperature, humidity, and physical impact, for example (e.g., hermetic sealing). In order to provide protection against the external electromagnetic radiation, the external shields are formed of electrically conductive material, typically metal. The bottoms of the circuit packages are typically not shielded by the external shield layers, although the substrate itself, external connecting pins protruding from the substrate and/or various electronic components, transmission lines and other circuitry within the substrate generally may provide some external shielding from external electromagnetic radiation. The external shield layers together with the bottom shielding together provide a “global shield” for the module.
One drawback of the external shield covering the circuit package is that it provides no shielding of individual electronic components from internally generated electromagnetic radiation (“internal electromagnetic radiation”) produced by other electronic components within the circuit package, causing electromagnetic interference, such as capacitive and inductive coupling and other cross-talk. Indeed, the external shield, in some cases, may aggravate the electromagnetic interference by reflecting the internal electromagnetic radiation back toward the electronic components within the circuit package. Another related drawback of the external shield is that it restricts design freedom required to optimize for best shielding for each of the individual electronic components, device placement within the module and overall module size.
Accordingly, there is a need for enhanced shielding among and between electronic components within a shielded circuit package or module, which does not unduly restrict design freedom with regard to placement of the electronic components, size of the module and other features.